[jira] [Commented] (HBASE-6900) RegionScanner.reseek() creates NPE when a flush or compaction happens before the reseek.

["Hudson (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-6900?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13490370#comment-13490370 ] 

Hudson commented on HBASE-6900:
-------------------------------

Integrated in HBase-0.94-security-on-Hadoop-23 #9 (See [https://builds.apache.org/job/HBase-0.94-security-on-Hadoop-23/9/])
    HBASE-6900 RegionScanner.reseek() creates NPE when a flush or compaction happens before the reseek. (Revision 1394378)

     Result = FAILURE
larsh : 
Files : 
* /hbase/branches/0.94/src/main/java/org/apache/hadoop/hbase/regionserver/StoreScanner.java
* /hbase/branches/0.94/src/test/java/org/apache/hadoop/hbase/regionserver/TestHRegion.java

                
> RegionScanner.reseek() creates NPE when a flush or compaction happens before the reseek.
> ----------------------------------------------------------------------------------------
>
>                 Key: HBASE-6900
>                 URL: https://issues.apache.org/jira/browse/HBASE-6900
>             Project: HBase
>          Issue Type: Bug
>            Reporter: ramkrishna.s.vasudevan
>            Assignee: ramkrishna.s.vasudevan
>             Fix For: 0.94.2, 0.96.0
>
>         Attachments: 6900-test.txt, HBASE-6900_1.patch, HBASE-6900.patch
>
>
> HBASE-5520 introduced reseek() on the RegionScanner.  
> Now when a scanner is created we have the StoreScanner heap.  After this if a flush or compaction happens parallely all the StoreScannerObservers are cleared so that whenever a new next() call happens we tend to recreate the scanner based on the latest store files.
> The reseek() in StoreScanner expects the heap not to be null because always reseek would be called from next()
> {code}
> public synchronized boolean reseek(KeyValue kv) throws IOException {
>     //Heap cannot be null, because this is only called from next() which
>     //guarantees that heap will never be null before this call.
>     if (explicitColumnQuery && lazySeekEnabledGlobally) {
>       return heap.requestSeek(kv, true, useRowColBloom);
>     } else {
>       return heap.reseek(kv);
>     }
>   }
> {code}
> Now when we call RegionScanner.reseek() directly using CPs we tend to get a NPE.  In our case it happened when a major compaction was going on.  I will also attach a testcase to show the problem.

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